Greenpeace believes that the toxic cargo on board the stricken Italian-registered tanker poses a real threat to marine life.

Four thousand tonnes of styrene, a colourless liquid used in the making of polystyrene and as a fibreglass resin, is seen as the most dangerous part of that cargo.

The chemical, which carcinogenic, is also only slightly soluble in water and very corrosive.

After initial hopes that the Ievoli Sun's cargo might remain contained as the ship sank intact, there have been reports that chemicals and fuel are now leaking.

The Guernsey authorities are playing down the seriousness of the incident and say pockets of Styrene spotted near the wreck should evaporate without causing any serious harm to the marine environment.

But Paul Johnston, Principal Scientist with Greenpeace in the UK, says a spill could spell further disaster for a coastline already devastated by last year's major oil spill from the oil tanker Erika.

'Worst case scenario'

"Styrene is our biggest concern there could be a major sea pollution incident," Dr Johnson said.

Wildlife was devastated by the Erika disaster

"The worst case scenario is that there could be a lasting affect on flora and fauna."

"The best we can hope for is that if the cargo is successfully savaged or that the styrene it comes out slowly," he added.

Dr Johnson says that although the present rough seas are good for dispersal, the weather conditions also make salvage more difficult and if the cargo escapes in large amounts a styrene slick could cause a lot of damage.

Damage feared

It is toxic and in tests on animals it can cause brain and liver damage if swallowed in sufficient quantities.

Breathing styrene vapour is known to produce symptoms such as nausea and irritation to the eyes in humans.

While styrene does not dissolve in water, it does disperse and will slowly break down into harmless by-products.

But this process could take a matter of weeks or months during which amounts of the toxic chemical will remain in the water.

Chris Finch, member of the Society of Chemical Industry told the BBC that the styrene would enter the food chain for a matter of weeks and it was possible that fish caught and eaten in that time could pose a threat to people's health.